Printing plate and cylinder



Aug. 11, 1959 E. A. CRAWFORD PRINTING PLATE AND CYLINDER 2 Sheets-Sheet 1 Filed April 9, 1957 INVENTOR. EARL A. CRAWFORD ATTOR EY Aug. 11, 1959 E. A. CRAWFORD.

PRINTING PLATE AND CYLINDER 2 Sh'eets-Shet 2 Filed April 9, 1957 INVENTOR. EARL A. CRAWFORD ATTORN PRINTING PLATE AND CYLINDER Earl A. Crawford, Warwick, RI.

Application April 9, 1957, Serial No. 651,641

18 Claims. (Cl. 101-4151) My present invention relates to the printing art, and more particularly to a novel construction of a printing plate and cylinder therefor.

The principal object of the present invention is to provide an improved plate and cylinder for holding a flexible printing plate in proper register and in close adherence to the cylinder.

Another object of the present invention is to provide a printing plate and cylinder having improved interlocking portions and firmer support for the plate.

A further object of the present invention is to provide a printing plate and cylinder in which the clamping line is reduced to a and held within the periphery of the plate.

Another object of the present invention is to provide a printing plate and cylinder which are easy to handle and clamp in position and in which the plate will remain in registry regardless of the clamping action.

A further object of the present invention is to provide a printing plate and cylinder which are simple in construction and easy and economical to manufacture and assemble.

With the above and other objects and advantageous features in view, my invention consists of a novel arrangement of parts more fully disclosed in the detailed description following, in conjunction with the accompanying drawings, and more particularly defined in the appended claims.

In the drawings,

Fig. 1 is a plan view of a printing cylinder with the clamp lock in closed position.

Fig. 2 is a similar View with the lock in open position.

Fig. 3 is an enlarged fragmentary section taken on line 33 on Fig. 2.

Fig. 4 is a similar section taken on line 4--4 on Fig. 1.

Fig. 5 is an exploded perspective view of the clamp lock.

Fig. 6 is a fragmentary perspective view of the plate.

Fig. 7 is an edge view of the plate.

The present invention particularly relates to dry offset, rotogravure and Wet offset printing presses, more specifically of the continuous web fed, roll to roll or roll to sheet type. In this type of printing an extremely thin flexible sheet is processed fiat and then wrapped around the cylinder with the free ends abutting. The plate must conform accurately to the surface of the cylinder and the free ends must be drawn tightly together. For economical continuous printing the unprinted gap must be reduced to a fine thin line. Various types of clamping mechanisms have been devised but it is believed that the one shown herein is superior in operation and perforn1- ance. Furthermore, the clamping action results in certain undesirable characteristics which have been eliminated by the plate of the present invention.

The plate of the present invention forms a seal which prevents the ink from penetrating the cylinder lock mechanism. This same seal resists the creeping and buckling inherent in all clamping actions at the clamping 2,898,854 Patented Aug. 11, 1959 line. Furthermore, the plate of the present invention is more easily clamped into position in proper register and can be easily removed and stored. While the plate of the present invention could be used on cylinders having other types of clamping locks with some alterations, the

,clamp lock shown and described herein is especially adapted for the plate of the present invention.

Referring more in detail to the drawings, the printing cylinder 10 is mounted on a shaft 11. The cylinder 10 is provided with a rectangular cutout portion 12 the length of the cylinder and parallel to the shaft 11. Referring to Figs. 3 and 4, the rear wall 13 of the cutout portion 12 is undercut so that it forms an acute angle with the surface of the cylinder. The front wall 14 is also undercut at an angle of approximately 7 /2 degrees. Beneath the cutout portion 12 is a flat rectangular slot 15 extending longitudinally of the cylinder and of sufficient width to extend under and beyond the rear wall portion 13 and front wall portion 14. Mounted in the cutout portion 12 is an elongated generally rectangular wedge member 16. The wedge member 16 rests on a rectangular block or platform 17 which is positioned in the slot 15. The platform 17 is comparatively small and supports the wedge member 16 at its center as shown in Fig. 5. The rear edge of the member 16 is cut at an angle to fit against the undercut rear wall 13 as shown in Fig. 3. The platform 17 is substantially the thickness of the slot 15 and the wedge member 16 is substantially the thickness of the cylinder from the slot 15 to the surface. The front edge of the member 16 is cut to form spaced blocks 18 having slanted wedge surfaces 19 and llat tops 20. For the best locking effect it is preferred that the portions 19 be at an angle of approximately 30 degrees.

Mounted adjacent the wedge member 16 is a similar elongated lock jaw member 21 having complementary platforms 22 at its rear edge interlocking with the platforms 18. The front edge 23 is undercut at an angle of 7 /2 degrees so that when it abuts the front wall 14 of the cutout 12 an inverted V-shaped space is formed with an angle of approximately 15 degrees. The jaw member 21 rests on a pair of spaced flat rectangular blocks 24, one under each end. The front edge of each block 24 is provided with cutout corners 25. An arcuate leaf spring 26 is provided with straight ends 27 which enter the cutout portions 25 and resiliently retain the blocks 24 in spaced relation to the front end wall of the slot 15 as shown in Figs. 3 and 4. Referring to Fig. 5 it should be noted that the width of the block 17 is less than the spacing between the block 25 so that longitudinal movement of the block 17 can be made as shown in dotted I lines in Figs. 1 and 2.

At each end of the cutout portion 12 and slot 15 is a rectangular block 28 having an integral flat base 29 equal to the width of the slot 15 so that it is slidable therein from each end and an upper narrow portion 30 which extends from the rear edge of the cutout portion 12 to a point short of the front edge leaving a slot or opening 31, as shown in Figs. 1 and 2. The blocks 28 are held in place by screws 32 extending vertically through openings 33 in the block. A set screw 34 extends laterally through each block bearing against the ends of the wedge member 16. As can be seen in Figs. 1 and 2, the jaw member 21 is slightly longer than the wedge member 16 and with the parts assembled the blocks 28 will prevent longitudinal movement of the jaw member 21 but will permit lateral movement of the jaw member. The set screws 34 are used to move the wedge member 16 longitudinally. When one screw is loosened and the other one tightened the wedge member will slide in one direction and if the screws are reversed the wedge member will be pushed in the other direction.

In preparing the cylinder 10 the wedge member 16 and jaw member 21 are moved to the locking position shown in Fig. l and the cylinder is then turned down to a perfect circle so that the jaw member 21 will form a perfect cylindrical support in its locking position. Since the movement of the jaw is rearwardly in a straight line and not annular, there will be a slight lifting effect in the open position shown in Figs. 2 and 3. One of the many problems with this type of cylinder is the necessity of properly supporting the plate at all possible points. Normally when the locking jaw is moved into locking position it will close the gap to a thin line but leave an opening behind it. This opening forms an unsupported portion extending across the plate and will result in a light spot in the impression. By forming the wedge members as illustrated in Fig. 5, the upsupported portion is broken up as shown in Fig. 1 into a series of small Z-shaped openings spaced from each other to provide a maximum amount of support. There is no solid unsupported line across the cylinder.

The plate construction is shown in Figs. 3, 4 and 6. The plate 35 is formed from a very thin sheet of metal ranging from .005 to .015 in thickness. The sheet must be thin enough and flexible enough to wrap around and accurately conform to the radius of the cylinder surface when locked in place. The plate 35 is formed so that one free edge 36 is bent downwardly and then upwardly into a U-shaped hook. The opposite free edge 37 is similarly bent to form a second U-shaped hook. The hook portion 36 is slightly wider than the hook portion 37 so that one can nest inside of the other. It should also be noted that the plate 35 is slightly longer than the cylinder as shown in dotted lines in Figs. 1 and 2.

When the plate 35 is mounted on the cylinder the wedge member 16 is drawn downwardly as in Fig. 2 by loosening the bottom set screw 34 and tightening the upper set screw 34. The springs 26 will then move the jaw member 21 to the right into open position. The U- portion 36 is slipped into the open slot and it will be noted that the slot 31 formed by the block 28 at each end will allow the longer plate to slip into place. The other U-portion 37 is now pushed into the slot and nests inside of the portion 36. The front wall 23 of the jaw member and the front edge 14 of the cutout portion 13 form an inverted Vshaped 15 degree space to accommodate the portions 36 and 37, see Fig. 3. I now provide a tie lock 38 which comprises a length of soft round wire approximately A inch in diameter One end of the wire 38 is provided with a head 39 and the other end is provided with a bent over manually engageable portion 40. The wire 38 may be slightly longer than the plate 35. The wire is pushed into the slot until it is positioned at the bottom of the U-bends as shown in Fig. 3.

Now referring to Figs. 1 and 4, the top set screw 34 is loosened and the bottom set screw 34 is tightened moving the wedge member 16 upwardly. The interlocking angular wedge surfaces 19 will force the jaw member 21 to the left against the action of the springs 26. As the jaw moves to the left the pressure will tend to tighten the plate 35 on the cylinder 10. In conventional constructions it has been found that a creeping action develops which normally forces the plate material upwardly at the edges. Where the ends of the plate have been clamped down below the surface of the cylinder there is not sufficient give to the plate and it will crack or tear. In the present invention the U-portions 36 and 37 will be crushed around the wire 38 to form a locking seal. However, this arrangement has enough give to allow the metal to creep upwardly to prevent breaking or tearing but not enough to form a bulge at the surface In locked position, as shown in Fig. 4, it is evident that no ink can seep between the jaws to foul the cylinder since the interlocked U-shaped portions 36 and 37 with the wire 38 form a perfect seal. With this type of plate it is essential that the different colors register perfectly. When the plate is inserted there must be a 4 fixed locating point for each plate. In the cylinder described herein the front wall 14 of the cutout portion 13 is immovable. This therefore forms the locating point. The tightening action is accomplished by the movement of the jaw 21. The plate 35 will therefore always register in the same place.

To remove the plate 35 the wedge member 16 is first moved downwardly into the position shown in Fig. 2 and the springs 26 will move the jaw 21 to the right. As this movement takes place the jaw 21 will cause a slight lifting of the cylinder near one edge and break the gripping seal between the plate and the cylinder. The plate is now loose. If it is desired to store it in its circular form, the shaft 11 and cylinder 10 is removed from the press and the plate slipped off endwise sliding through the slots 31 and leaving the U-shaped portions 36 and 37 interlocked around the wire 38. If it is desired to store the plates flat and unlock them, the portion 40 of the wire is grasped and pulled upwardly like a rip cord or tear strip. As the wire 38 is pulled upwardly it spreads the arms of the U-shaped portions 36 and 37 so that they can be lifted out one from the other.

By the use of the plate and cylinder of the present invention certain advantages over conventional plates and cylinders are obtainable. The closing jaw forms an accurate surface radius giving the plate an even perfect support. When the jaw retracts in a straight line it breaks the continuity and releases the surface tension of the plate making it quick and easy to remove. The opposing angles at the jaw counters the plate surface resistance caused by the advancing bar. This also creates a self-adjusting or compensating drawing action which prevents the plate from creeping out. The interlocking ends of the plate are not fixed and they will yield to the downward pressure created by the angle of the creeping walls. As the jaw closes the ends want to pull out of the slot but the angular pressure keeps forcing the ends downwardly and locking them tighter in place. The interlocking ends thus serve to tighten the plate in place to form a perfect cylinder with suflicient yielding action to prevent breaking.

Another great advantage of the present plate and cylinder is the speed'with which a job can be made ready or altered. This reduces the time and expense during which the press is idle. For example, rubber plates are normally glued or vulcanized directly on the cylinder. If the impression is weak at one spot then the contacting roller must be brought up closer with the result that the strong spots have too much pressure. By utilizing the present invention the rubber can be attached to the plate and weak spots can be brought up by loosening the plate and sliding a sheet under the spot to lift it.

Another advantage of the present invention is that it permits a plurality of plates to be placed on a single cylinder. In multiple jobs where a single main design is used with variations, one or more of the plates can be removed and changed without disturbing the rest of the cylinder. This permits short runs of changing designs with a minimum of time lost between changes. Other advantages of the present invention will be readily apparent to a person skilled in the art.

I claim:

1. In combination a printing cylinder, a thin flexible printing plate Wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a generally rectangular gap in the surface of said cylinder, a movable jaw slidable on the bottom of said gap and against one side wall thereof for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said U-bends being frictionally clamped between said movable jaw and said gap wall when said jaw is in clamping position.

2. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a generally rectangular gap in the surface of said cylinder, a movable jaw slidable on the bottom of said gap and against one side wall thereof for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said U-bends being frictionally clamped between said movable jaw and said gap wall when said jaw is in clamping position.

3. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, a movable jaw for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said releasing means including a soft wire extending along the bottom of said nested U-bends.

4. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, a movable jaw for closing said cylinder gap, the free ends of said Plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said releasing means including a soft wire extending along the bottom of said nested U- bends, said wire being longer than the Width of said plate and having a finger engageable portion for pulling said wire from said U-bends after the opening of said aw.

5. In combination a printing cylinder, a thin flexible plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder having a flat bottom portionundercutting the walls of said gap, a plurality of flat plates slidably mounted on the bottom of said gap, a movable jaw mounted on said flat plates for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said moving means comprising a wedge member mounted on flat plates in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces.

6. In combination a printing cylinder, a thin flexible plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder having a flat bottom portion under- 6 cutting the walls of said gap, a plurality of flat plates slidably mounted on the bottom of said gap, a movable jaw mounted on said flat plates for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said moving means comprising a wedge member mounted on flat plates in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw.

7. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder having a fiat bottom, a movable jaw slidable on said flat bottom and against one side wall of said gap for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said moving means comprising a wedge member in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces, said U-bends being frictionally clamped between said movable jaw and said gap wall when said jaw is in clamping position.

8. In combination a printing cylinder, a thin flexible printing plate Wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder having a flat bottom, a movable jaw slidable on said flat bottom and against one side wall of said gap for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder,

said moving means comprising a wedge member in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said U-bends: being frictionally clamped between said movable jaw and said gap wall when said jaw is in clamping position.

9. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, a movable jaw for closing said cylinder gap, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said moving means comprising a wedge member in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said releasing means including a soft wire extending along the bottom of said nested U- bends.

10. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, a movable jaw for closing said cylinder gap, the free ends of said plate being bent down wardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one with-v in the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said moving means comprising a wedge member in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said releasing means including a soft wire extending along the bottom of said nested U-bends, said wire being longer than the width of said plate and having a finger engageable portion for pulling said wire from said U- bends after the opening of said jaw.

11. In combination a printing cylinder, a thin flexible plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a generally rectangular gap in the surface of said cylinder, a movable jaw slidable on the bottom of said gap for closing said cylinder gap, said jaw being movable against a fixed wall of said gap, said wall and jaw being undercut to form an inverted V-shaped opening therebetween, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said interlocking means being frictionally retained in said inverted V-shaped opening when said jaw is in clamping position.

12. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a generally rectangular gap in the surface of said cylinder, a movable jaw slidable on the bottom of said gap for closing said cylinder, said jaw being movable against a fixed wall of said gap, said wall and jaw being undercut to form an inverted V-shaped opening therebetween, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said interlocking means being frictionally retained in said inverted V-shaped opening when said jaw is in clamping position.

13. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder having a flat bottom, a movable jaw slidable on the bottom of said gap for closing said cylinder gap, said jaw being movable against a fixed wall of said gap, said wall and jaw being undercut to form an inverted V-shaped opening therebetween, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U- bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said interlocked U-bends being squeezed between said inverted V-shaped walls of said fixed wall and movable 14. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder having a flat bottom, a movable jaw slidable on the bottom of said gap for closing said cylinder gap, said jaw being movable against a fixed wall of said gap, said wall and jaw being undercut to form an inverted V-shaped opening therebetween, the

free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said interlocked U-bends being squeezed between said inverted V-shaped walls of said fixed wall and movable jaw.

15. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, a movable jaw for closing said cylinder gap, said jaw being movable against a fixed Wall of said ga said wall and jaw being undercut to form an inverted V-shaped opening therebetween, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said releasing means including a soft wire extending along the bottom of said nested U-bends.

16. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, a movable jaw for closing said cylinder gap, said jaw being movable against a fixed wall of said gap, said wall and jaw being undercut to form an inverted V-shaped opening therebetween, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U-bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said releasing means including a soft wire extending along the bottom of said nested U-bends, said wire being longer than the width of said plate and having a finger engageable portion for pulling said wire from said U-bends after the opening of said jaw.

17. In combination a printing cylinder, a thin flexible plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, said gap having a flat bottom unr dercutting the walls of said gap, a plurality of flat plates slidably mounted on said flat bottom, a movable jaw mounted on said flat plates for closing said cylinder gap, said jaw bein" movable against a fixed wall of said gap, said wall and jaw being undercut to form an inverted V-shapecl opening therebetween, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, and means for moving said jaw into clamping position to clamp said interlocking plate portions in said cylinder, said moving means comprising a wedge member mounted on flat plates in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces.

18. In combination a printing cylinder, a thin flexible printing plate wrapped around said cylinder, plate clamping mechanism in the cylinder comprising a gap in the surface of said cylinder, a movable jaw for closing said cylinder gap, said jaw being movable against a fixed wall of said gap, said wall and jaw being undercut to form an inverted V-shaped opening therebetween, the free ends of said plate being bent downwardly to extend into said gap, means for interlocking the free ends of said plate in said gap, said interlocking means comprising a U1 bend at the bottom edge of said downwardly bent portions, said U-bends nesting one within the other, and means for moving said jaJw into clamping position to clamp said interlocking plate portions in said cylinder, said moving means comprising a wedge member in said gap behind said jaw, said wedge member and jaw having complementary intermeshing wedge surfaces, and means for releasing said interlocked portions of said plate after the opening of said clamping jaw, said releasing means including a soft wire extending along the bottom of said nested U-bends, said wire being longer than the width of said plate and having a finger engageable portion for pulling 'said wire from said U-bends after the opening of said jaw.

References Cited in the file of this patent UNITED STATES PATENTS Forbes Apr. 8, 1890 Gardner et a1 Aug. 18, 1914 Wagner et al. Feb. 23, 1915 Gamble et al. June 12, 1923 Pritchard Oct. 13, 1931 Harrold Apr. 12, 1932 Gietz Mar. 14, 1933 Walmsley Apr. 26, 1938 Kerr et al. May 31, 1938 Grupe Mar. 19, 1940 Sheeler et a1. May 7, 1940 Worthington Mar. 25, 1941 Boyojean June 9, 1953 FOREIGN PATENTS Germany Aug. 30, 1935 Switzerland July 15, 1950 

